1. Field of the Invention
The present invention relates to a heat sink, a cooling member, a semiconductor-substrate cooling system, a computer, and a radiation method, and more particularly to an apparatus, method and system for efficiently radiating heat generated in a CPU, or the like, of a computer.
2. Description of Related Art
As is known, because a temperature rise of a central processing unit (hereafter referred to as CPU) of a computer is directly related to the performance of the CPU, it is often desirable to attempt to diffuse the heat generated in the CPU and cool the CPU.
To improve cooling of the CPU, it is often necessary to increase the size of a radiating portion to be situated in relation to the CPU so as to contact to allow heat transfer. It is also known to position a fan in close proximity to the CPU such that the fan may provide air flow to a radiating portion, and/or the rotational speed of the fan may be increased to increase air flow. However, each of these options, increasing the size of the radiating portion and the fan, and increasing the rotational speed of the fan, are not preferred implementations as the former opposes the present trends of downsizing computer footprints and sizes, and the latter causes additional problems such as noise.
As shown in FIGS. 9 and 10, a heat sink 101 is set forth radiates heat generated in a CPU. FIG. 9 is an illustration showing a structure of the heat sink 101 and FIG. 10 is a sectional view taken along a line Vxe2x80x94V in FIG. 9. As shown in FIG. 9, the heat sink 101 is constituted by integrally forming a radiating portion 102 for radiating and diffusing the heat generated in a CPU and a centrifugal-fan-type blasting portion 103 for blasting air to the radiating portion 102. The radiating portion 102 is provided with a substrate portion 104 formed of a flat member made of copper, a radiating fin 106 protruded to one flat face 104a of the substrate portion 104, both end margins 104b of the substrate portion 104, and a side-plate portion 107 rising from the both margin ends 104b. Moreover, as shown in FIG. 10, the radiating portion 102 is provided with an upper-plate portion 108 formed so as to cover the substrate portion 104 from the top. Therefore, as shown in FIG. 10, the radiating portion 102 forms a duct-like space 112 for the substrate portion 104, side-plate portion 107, and upper-plate portion 108 to surround the radiating fin 106. Moreover, as shown in FIG. 10, the heat sink 101 is positioned so that a CPU 111 provided on the motherboard 110 of the computer directly contacts a flat face 104c opposite to a flat face 104a of the substrate portion 104.
At the time of driving the blasting portion 103 while setting the heat sink 101 as shown in FIG. 10, an airflow generated by the blasting portion 103 passes through the duct-like space 112 and exhausted to the outside from the exit portion 112a (refer to FIG. 10) of the duct-like space 112. However, the heat generated in the CPU 111 is conducted to the substrate portion 104 and moreover conducted up to the radiating fin 106. In this case, because the substrate portion 104 and radiating fin 106 are cooled by the airflow supplied from the centrifugal fan, it is possible to diffuse the heat generated in the CPU 111.
The centrifugal-fan-type blasting portion 103 is constituted so as to blast air in Y direction tilted by a predetermined angle from X direction which is an extending direction of the radiating portion 102 (extending direction of the duct-like space 112) as shown in FIG. 9. However, to maximize a radiation effect, the radiating fin 106 is formed on the entire surface of the substrate portion 104 and the air resistance along the substrate portion 104 in the duct-like space 112 is almost uniform. Therefore, at the time of driving the blasting portion 103, a portion where an airflow occurs is restricted to a portion to which air is directly blasted from the blasting portion 103 (e.g. area a in FIG. 9) and air stays in a portion (e.g. area b in FIG. 9) deviated from the blasting direction (Y direction) viewed from the blasting portion 103.
However, as it is difficult to completely cool the radiating fin 106 at a portion deviated from the blasting direction (Y direction) viewed from the blasting portion 103, the cooling performance is less than that desired.
Moreover, since it is impossible to completely cool the portion deviated from the blasting direction (Y direction) as described above, a temperature rise occurs at this portion and heat is conducted up to the housing of the computer through a screwed portion 113 formed on the radiating portion 102. For such a situation, the surface temperature of the computer housing rises and availability of a user may be lost.
Accordingly, there is a need for an apparatus, method and system that overcomes the problems discussed above. The present invention provides an apparatus, method and system having efficient cooling performance, even for a compact structure, while suppressing a temperature rise of the housing of a computer.
According to one embodiment, the present invention is a heat sink, comprising: a radiating plate for radiating heat conducted from a heat source; a ventilation area formed along said radiating plate; and a blasting fan for blasting air to said ventilation area, wherein a high-wind-pressure portion and a low-wind-pressure portion having wind pressures different from each other when air is blasted by the blasting fan are formed in the ventilation area and wind-force losing members for losing the wind pressures are provided for the ventilation area, and the wind-force losing members are densely provided for the high-wind-pressure portion compared to the low-wind-pressure portion.
In this embodiment, because the high-wind-pressure portion has a large pressure loss and the low-wind-pressure portion has a small pressure loss in the ventilation area, wind pressures in the ventilation area are averaged. Therefore, rates of airflows generated by the blasting fan are averaged in the ventilation area and as a result, an airflow is generated in any portion in the ventilation area. In this case, it is possible to use a radiating fin or the like for radiation as a wind-force-losing member.
In this embodiment, when the ventilation area is formed like a duct, the blasting direction by the blasting fan tilts by a predetermined angle from the extending direction of the ventilation area, the high-wind-pressure portion is provided in the blasting direction of the blasting fan viewed from the blasting fan, and the low-wind-pressure portion is provided in a direction other than the blasting direction viewed from the blasting fan, it is possible to set a blasting direction independently of the extending direction of the duct-like ventilation area. Additionally, as used herein, the term xe2x80x9cduct-likexe2x80x9d includes not only a completely cylindrical shape but also a half-duct-like shape, that is, a half-cylindrical shape.
Moreover, when the low-wind-pressure portion is provided for separate positions at the both sides of the high-wind-pressure portion viewed from a tangential line of the blasting direction to the blasting fan, an airflow along the blasting-directional tangent also moves to the low-wind-pressure side and air is blasted to both the high- and low-wind-pressure portions.
Furthermore, when a portion of the radiating plate facing the low-wind-pressure portion is flatly formed, it is possible to minimize the pressure loss of this portion. Therefore, it is possible to easily generate a pressure-loss difference between the low- and high-wind-pressure portions by providing the wind-force losing member for the only high-wind-pressure portion.
Furthermore, the present invention, in a further embodiment, is a cooling member having a cooling member body contacting a heat source and forming a duct-like structure and a plurality of radiating fins fixed to the cooling-member body and protruded to the inside of the duct-like structure in which a high-density area and a low-density area different from each other in radiating-fin arrangement density are formed.
In this embodiment, by making radiating-fin arrangement densities different in the duct-like structure, a portion having a large air resistance and a portion having a small air resistance are formed in the duct-like structure and thereby a pressure loss is made different for each portion and thus, it is possible to suppress a flow-rate difference due to the difference between wind pressures working in the duct-like structure. Therefore, particularly when an airflow having a direction intersecting with the extending direction of the duct-like structure is generated in the duct-like structure, it is preferable to form the high-density area in an air-flow generation area and the low-density area in a portion other than the generation area.
In this embodiment, airflow is generated through blasting by a blasting fan or through attraction of air by any attracting means. Moreover, the duct-like structure includes not only a perfect cylindrical shape but also a half-duct shape, that is, a semi-cylindrical shape.
Moreover, in this embodiment, when a radiating fin is positioned so as to extend in the direction same as the extending direction of the duct-like structure, the extending direction of the radiating film tilts from a blasting direction. Also in this case, however, it is possible to uniform the flow rate in the duct-like structure.
Furthermore, when the extending direction of a radiating fin tilts toward the low-density area rather than an air-flow generating direction viewed from an air-flow generating area, it is possible to attract an airflow toward the low-pressure low-density area deviated from the air-flow generating area and therefore, it is possible to preferably pass the airflow along the radiating fin.
In a further embodiment, the present invention can be regarded a semiconductor-substrate cooling system comprising a radiating member having a flat portion and a centrifugal fan set adjacently to the radiating member, in which the nozzle of the centrifugal fan opens at one end margin of the flat face of the flat portion and the flat face of the flat portion has a high-resistance area and a low-resistance area having air resistances different from each other when air is blasted from the centrifugal fan.
Thus, by forming portions having air resistances different from each other on the flat face of the flat portion of a radiating member, it is possible to uniform a flow rate because of the difference between air resistances even if an airflow generated by the centrifugal fan acts on the radiating member in a non-uniform manner.
Moreover, in this embodiment, by forming the high-resistance area in the blasting direction by the centrifugal fan viewed from the nozzle of the centrifugal fan and the low-resistance area at the high-resistance area side viewed from the blasting direction, it is possible to supply some of the airflow generated by the centrifugal fan not only to the high-resistance area but also to the low-pressure low-resistance area.
Furthermore, at the time of forming the high-resistance area so that its width viewed from the nozzle becomes almost equal to the diameter of the centrifugal fan, even if enlarging the radiating member compared to the diameter of the centrifugal fan, it is possible to preferably supply an airflow to the whole radiating member by using the enlarged portion as the low-resistance area.
Furthermore, in a further embodiment, the present invention is a computer having a central processing unit for performing operations, a cooling system for cooling the central processing unit, and a housing for housing the central processing unit and the cooling system, in which the cooling system contacts the central processing unit and has a radiating member having a flat portion and a blasting portion for blasting air to the plat face of the flat portion and the flat portion is formed so that the roughness of the plat face of the flat portion differs in accordance with the difference between wind pressures working when air is blasted by a blasting portion.
According to the above embodiment, as configured, it is possible to uniformly cool the radiating member of the cooling system and suppress the temperature of the central processing unit.
Moreover, when fins are arranged on the flat face of the flat portion of the radiating member of the cooling system, it is possible to easily adjust the roughness of the flat-portion surface by adjusting the roughness of the flat face of the flat portion in accordance with the arrangement density of the arranged fins.
Furthermore, in this embodiment, if areas having a roughness different from each other are adjacently arranged viewed from the extending direction of a fin, it is possible to generate an airflow from a blasting portion in directions other than the extending direction of the fin by using the difference between air-flow pressure losses due to the difference between each roughness.
Furthermore, in this embodiment, when the blasting portion and the radiating portion are integrally formed, it is possible to downsize the cooling system.
Furthermore, in a still further embodiment, the present invention is a radiating method of radiating the heat conducted from a heat source by using a radiating member, comprising forming the surface of a radiating member so that the air resistance of a part of the surface becomes smaller than that of other portion and generating an airflow along the surface of the radiating member toward the other portion so that the airflow passes through the part of the surface decreased in air resistance and also flows in the direction intersecting with the air-flow generating direction.
Thus, at the time of blasting air to the radiating member, it is possible to decrease the air resistance of a part of the radiating member and use the part as a path for preferably supplying air to the whole radiating member.